The present invention relates to a combinatorial weighing apparatus and, more particularly, to a combinatorial weighing apparatus of the type having a plurality of weighing hoppers and adapted for weighing articles through the steps of finding the weight of batch of article in each weighing hopper, selecting the combination of weighing hoppers which gives a total weight equal to or closest to a present target weight (hereafter referred to as the "best" combination) and discharging the batches of article from the weighing hoppers constituting the selected combination.
Generally, a combined weighing apparatus incorporating a computer, referred to as "computer scale", is used for accurately weighing articles which exhibit large variation in weight from one to another, e.g. fruits and vegetables, confectionaries, fabricated articles, perishables or the like.
In such a combinatorial weighing apparatus as shown in FIG. 1, batches of the article to be weighed are put into a plurality of weighing hoppers 2d and weighed in respective hoppers by weight sensors 3. Then, the apparatus selects a combination of batches which provides a total weight closest to the target weight within a predetermined tolerance using the weighing outputs derived from the weight sensors 3. The batches constituting the selected combination are then discharged into a collecting hopper 5 and the evacuated weighing hoppers are charged with new batches of the article for the next cycle of weighing operation. This operation is repeated to achieve the automatic weighing of the article.
Referring to FIG. 2 schematically showing the mechanism of a combinatorial weighing apparatus, a distribution table 1 is adapted to disperse the article to be weighed in the radial direction and to distribute the dispersed batches of article to a plurality of weighing stations 2 arranged radially around the distribution table 1. The distribution table 1 is adapted to be vibrated by a vibrator or the like, so that the dispersed article is distributed to the weighing stations 2 as a result of the vibration of the table for a predetermined time length. In the illustrated embodiments, n weighing stations designated at 2-1 to 2-n are arranged, and each weighing station includes a distribution supply device 2a, pool hopper 2b, pool hopper gate 2c, weighing hopper 2d, weight sensor 2e, weighing hopper gate 2f and a hopper drive unit 2g. As shown in FIG. 3, the distribution supply device 2a is composed of a feeder base 2a-1 having a predetermined shape and a trough 2a-2 mounted on the feeder base 2a-1 through a leaf spring 2a -4. A solenoid 2a-3 is fixed to the upper side of the leeder base 2a-1. A solenoid 2a-3 is mounted on the feeder base 2a-1. As will be seen from FIGS. 4 and 5, a plurality of distribution supply devices 2a are carried by a circular support member 4 through respective coiled springs 2a-5 and are arranged radially along the outer periphery of the distribution table 1. In operation, the article to be weighed is put on the distribution table 1 while the latter is vibrated reciprocatingly and spirally by an electromagnetic vibrator 6, so that the articles are dispersed radially outwardly along the conical top surface of the distribution table 1 into separate batches which in turn are delivered to respective troughs 2a-2. The batch of articles supplied to each trough 2a-2 is conveyed through the latter in the direction of the arrow in FIG. 3 as a result of a linear reciprocating vibration caused by the magnet 2a-3, and is put into the pool hopper 2b from the end of the trough 2a-2.
Referring back to FIG. 2, each pool hopper 2b is provided with a pool hopper gate 2c. As this pool hopper gate 2c is opened by the operation of the hooper drive unit 2g, the batch of article contained by the pool hopper 2b is put into the weighing hopper 2d. Each weighing hopper 2d is provided with a weight sensor 3 for weighing the batch of article put into the weighing hopper 2d. The output from the weight sensors 3 are delivered to a combination controlling section (not shown) which selects the best combination of the batches of article which provides a total weight most closely approximating the target weight within a predetermined tolerance. Each weighing hopper 2d is provided with a weighing hopper gate 2f. After the selection of the "best" combination, only the weighing hopper gates 2f of the weighing hoppers constituting the "best" combination are opened by the operation of the hopper driving device 2g to let the batches of article go out of these hoppers. These batches of article are then collected at the lower central portion of the weighing apparatus through a collecting chute 5. The collecting chute 5 has a form resembling a conical funnel, and the batches of article dropping onto the peripheral portions of the chute are gathered at the central portion thereof naturally by the force of gravity or forcibly by a scraping means (not shown) or the like.
At the initial stage of the weighing operation, the weighing hoppers 2d are charged with respective batches of articles to be weighed. The weight sensors 2e annexed to these weighing hoppers 2d weigh the batches of articles and deliver weight signals L.sub.1 to L.sub.10 to the combination control section which is not shown. The combination control section then makes a computation of total weight for various hopper combinations and selects a combination which provides a total weight most closely approximating the target weight within a predetermined tolerance. The hopper drive unit 2g then opens the weighing hopper gates of the weighing hoppers constituting the selected "best" combination. In consequence, the batches of articles providing the "best" combination are discharged from these hoppers 2d into the collecting chute 5. Then, the pool hopper gates 2c are opened to charge the evacuated weighing hoppers with new batches of articles. At the same time, the distribution supply devices 2a corresponding to the evacuated pool hoppers 2b are vibrated for a predetermined time to charge the empty pool hoppers 12b with the articles to be weighed. Then, the selection of the "best" combination is made in the same manner as that explained before. The weighing operation by the combinatorial weighing apparatus is thus performed repeatedly and continuously.
In this combinatorial weighing apparatus, a higher weighing accuracy is obtained as the number of combinatorial weighing cycle is increased. To this end, the known combinatorial weighing apparatus employed a lot of weighing sensors to obtain a greater number of weighing combinations, resulting undesirably in a larger size and complicated construction of the weighing apparatus as a whole. Moreover, the cost of the apparatus as a whole is uneconomically raised by employment of a large number of weight sensors which are generally expensive.